This invention relates to an apparatus for controlling movement of a throttle valve in response to a change in the position of an accelerator pedal.
In order to meter the amount of air to an internal combustion engine, a variable positionable throttle valve is situated within a throttle chamber connected to the engine induction passage. Normally, a mechanical link mechanism is provided to couple the throttle valve to an accelerator pedal or other accelerator device such as an accelerator lever in a manner to move the throttle valve in response to movement of the accelerator pedal. In order to improve the responsiveness of the movement of the throttle valve with respect to the movement of the accelerator pedal, it has been proposed to substitute an electrical servo control system for the mechanical link mechanism. Such an electrical servo control system includes a potentiometer which converts the movement of the accelerator pedal into a corresponding electric signal which is electrically processed to drive an actuator which thereby moves the throttle valve to a position corresponding to the new position of the accelerator pedal. The servo control system is powered from a vehicle battery through an ignition switch. Consequently, the servo control system stops its operation immediately when the driver turns the ignition switch off in order to bring the engine to a stop.
The throttle valve is urged toward its closed position by a return spring having a relatively great resilient force. If the driver turns the ignition switch off while depressing the accelerator pedal, the throttle valve will return rapidly to its closed position into abutment against the valve rest, causing the throttle rest to bit the throttle valve and/or to be subject to failure.
Therefore, the present invention provides an improved throttle valve control apparatus which can prevent the throttle valve from moving rapidly into abutment against the valve rest under a great force of the return spring when the driver turns the ignition witch off while depressing the accelerator device.